This PDF file contains the front matter associated with SPIE Proceedings Volume 12516, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Artificial Intelligence (AI) using ANNs (Artificial Neural Networks) and Inductively Coupled Plasma (ICP)-Optical Emission Spectrometry and microplasma-Optical emission Spectrometry be described in some detail. Also, the application of Deep Learning (DL) using a portable, fiber-optic spectrometer will be discussed. Potential applications of ChatGPT and Jasper.AI in spectroscopy will be highlighted.

The next generation of infrared spectroscopic solutions collect massive amounts of data that is realistically much too dense to be understood by a human. Thus, as a practical necessity, the user is generally interested in a smaller number of “critical” variables that aren’t directly observed. However, considering a more manageable subset of the raw data throws away a great deal of collected information. The problem of distilling the critical variables and related uncertainties from the raw data is one of statistical inference. We adopt a Bayesian approach to better quantify the uncertainties in the critical variables. This approach, when paired with an appropriate model of the hardware and the system being observed, can greatly improve the effective signal to noise and/or reduce the required measurement time.

Non-contact imaging modalities for monitoring wound health could supplement the current standard which is a visual inspection by clinicians. Recently, a smartphone oxygenation tool (SPOT) has been developed for physiological imaging of tissue oxygenation changes in response to treatment. However, upon visual inspection of the wound bed and surrounding area, there are variations of pigmentation. Melanin concentration is a highly absorbing chromophore that can impact spatial oxygenation measurements. The objective of this study was to classify the six Fitzpatrick Skin Types (FST) by applying deep learning techniques prior to correcting SPOT’s oxygenation maps. In this IRB-approved study, control subjects were imaged on seven skin locations of varying FST (I-VI) under three different lighting conditions using SPOT device’s camera. A benchmark dataset with samples of 28 × 28 pixel images of human subjects’ feet was developed in three color spaces (R-G-B, Y-Cb-Cr, L-a-b). A deep learning algorithm, specifically a convolutional neural network (CNN), was used to classify skin into six FST (classes). Preliminary results showed the skin types on control subjects’ feet could be classified using deep learning with hyperparameter tuning with accuracies of < 82%. Our ongoing efforts are focused on extensive in-vivo studies on control subjects of FST I-VI on feet towards future implementation of the technology for diabetic wounds and oxygenation mapping using the SPOT device. Keywords: Smartphone-based NIRS device, deep learning algorithms, Fitzpatrick skin types, wounds, melanin, tissue oxygenation, diabetic foot ulcers

Mid-infrared spectroscopy is often used to identify material. Thousands of spectral points are measured in a time-consuming process using expensive table-top instrument. However, material identification is a sparse problem, which in theory could be solved with just a few measurements. Here we exploit the sparsity of the problem and develop an ultra-fast, portable, and inexpensive method to identify materials. In a single-shot, a mid-infrared camera can identify materials based on their spectroscopic signatures. This method does not require prior calibration, making it robust and versatile in handling a broad range of materials.

The present review article considers the rapid development of miniaturized handheld near-infrared spectrometers over the last decade and provides a short overview of current instrumental developments and exemplary applications in the fields of material and food control. Care is taken, however, not to fall into the exaggerated and sometimes overoptimistic narrative of some direct-to-consumer companies, which has raised unrealistic expectations with full-bodied promises, but has harmed the very valuable technology of NIR spectroscopy, rather than promoting its further development. Particular attention is paid to potential applications that will enable a clientele that is not necessarily scientifically trained to solve quality control and authentication problems in everyday life with this technology in the not-too-distant future.

Echelle-inspired cross-grating spectrometers try to combine the high performance of classical Echelle spectrometers and the small footprint of compact line-grating spectrometers. Therefore, a cross-grating is used which is a superposition of two perpendicularly oriented line gratings in a single element. Highly resolved, but overlapping, diffractions orders are created by the main grating, which are separated by the cross-disperser. This powerful approach is connected to different challenges concerning the optical design, the fabrication of the cross-grating and implementation of the device. These challenges are addressed by a compact and rigid double-pass design, which utilizes the same refractive elements for collimation of the incoming beam and focusing of the diffracted light on the detector. This contribution gives an overview on the design and focusses on the implementation of the spectrometer. This includes on one hand the mounting of the cross-grating and the refractive elements in a rigid objective group and, on the other hand, the adjustment of the objective to the entrance fiber and the 2D detector. Furthermore, the implemented and calibrated instrument allows to conduct several validating experimental tests in order to proof the working principle. The spectrometer addresses a spectral range from 400 nm to 1100 nm and reaches a resolving power of 300 with an entrance pinhole diameter of 105 μm. An even higher resolving power of more than 1000 is reached with a reduced pinhole diameter of approximately 5 μm.

A variety of microplasmas have been fabricated and have characterized with a variety of samples, In this presentation, the application of microplasmas for chemical analysis purposes will be described in some detail.

Portable spectroscopy has been a rapidly growing field, being the subject of an extensive review in 2018. In 2021, the whole field of portable spectroscopy and spectrometry, from the technologies and instruments, through to field applications, required a two-volume book to do it justice. Progress in this field continues apace, with ever-smaller instruments and devices. Developments in other fields of optics and photonics are fueling this, and this paper summarizes some of the newer technologies being applied, and the technologies that could potentially be applied in the near future. Multispectral devices can be produced in volume via semiconductor and optical coating techniques, at very low cost - less than $10 each. Silicon photonics and photonic integrated circuits (PICs), produced en masse using semiconductor manufacturing techniques, are the ideal next step. This spectroscopic miniaturization, and concomitant cost reduction, has reached the point where multispectral sensors can now be incorporated into ‘fitness’ products like smart watches and sports watches, and into ‘wearables’ like smart rings, providing the user with health information, with several groups claiming they are close to a wearable non-invasive (i.e., optical) blood glucose device.

The development of rapid and sensitive detection technology for identifying of chemicals and biological agents such as contraband substances, narcotics and toxins is critical for decision-making among first responders and military personnel. Recent advances in nanofabrication, microelectronics and computational power have led to miniaturization of portable analytical instruments. Among these, handheld Raman analyzer coupled with Surface Enhanced Raman spectroscopy (SERS), have become increasingly common for field detection challenges due to the enormous sensitivity of SERS technique. In this paper, we demonstrate the fabrication and analysis of flexible and porous paper-based SERS sensors by inkjet printing of colloidal Au nanoparticles (AuNP) onto paper substrate. Our paper-based SERS sensors are cost-effective and robust, and they provide the added advantage of point-of-sampling capability that rigid SERS sensors lack. With their inherent filtration sampling capability, we coupled our paper-SERS sensors with air pump for active sampling and detection of chemical aerosols. Additionally, we printed the SERS sensors in test strip format to enable swab sampling of chemical contaminants on door handle as a simulated field-sampling and detection of chemical toxins. Our swab sampling successfully picked up enough benzenethiol, BPE and fentanyl molecules to trigger positive detection. The used swab can also be preserved for further confirmatory tests such as paper-spray mass spectrometry.

We are developing a vapor detection platform that combines the mixture separation power of gas chromatography with the identification power of infrared spectroscopy. The gas chromatography column is implemented using a meandering channel (imprinted in a molded lid) with the bottom of the channel consisting of a germanium wafer where an infrared laser is introduced in order to perform ATR IR spectroscopy along several segments of the column. We overcome the relative insensitivity of the ATR method by exploiting multiple bounces along the ATR wafer, as well as coating the wafer with a thin film of sorbent which adsorbs and concentrates the analyte in the evanescent region at the surface of the wafer. A unique advantage of our technique is that we collect signal from multiple points along the GC column (including the beginning) for rapid response. This is a major milestone towards implementing a complete micro-gas chromatography sensor for rapid analysis of complex chemical mixtures. Such technology is very attractive for early warning applications in defense and environmental monitoring.

We present further development of an eye-safe, invisible, stand-off technique designed for the detection of target chemicals (such as explosives) in a single “Snapshot” frame. Broadband Fabry-Perot quantum cascade lasers (FP-QCLs) are employed in the Mid-LWIR (long-wave infrared) in the range of 7 to 12 μm, to interrogate the spectral features from analytes of interest. We have developed a custom-built broadband laser source in the Mid-LWIR range. This “white” broadband laser source enables stand-off detection in a single snapshot frame. High power FP-QCLs with wide spectral coverage were collimated and aligned toward the target several meters away. The “backscatter” and absorption signals from target chemicals are spectrally extracted by an LWIR spectrometer based on the spatial heterodyne spectroscopy (SHS) technique or by a grating spectrometer. Both spectroscopic methods offer full spectral coverage in each single frame from an IR imaging array. This presentation will cover the implementation and optimization of FP-QCLs for this broadband spectroscopic application. We discuss the collection and processing of SHS images to extract spectral information. Finally, we present results of measurements using specific analytes to demonstrate the application of the method to stand-off detection of targets such as explosives and other chemical threats.

We have developed a miniaturized silicon photonics short-wave infrared spectrophotometer that fits in a wrist-based wearable device. Our device has the capability for non-invasive and real-time measurement of various physiologic biochemistries that cannot be interrogated with the same accuracy when using light emitting diodes (LEDs) and common photoplethysmography (PPG) applications. By producing many discrete and individually addressable laser diodes on a single photonics integrated circuit together with wavelength multiplexing and on-chip wavelength and power monitoring, our platform enables novel commercial applications, including the ability to sense hydration status, core body temperature, alcohol consumption, lactate threshold, and glucose levels.

Senorics develops and distributes novel highly integrated spectrometers in the near infrared spectral region. The innovation is based on organic electronics as it is well known for OLED displays. We demonstrate the latest dvelopments for high performance NIR sensors used in agricultural applications where extremely high precision is desired. On the other hand Senorics' sensors are implemented into hand held devices equipped with a mobile app and various application models e.g. textile identification and quantification and others. The route towards miniaturization allows even the integration in industry 4.0 applications or low-cost consumer electronics devices such as robotic vacuum cleaners or wasching machines.

We experimentally demonstrate a compact Fourier Transform on-chip spectrometer based on spatially heterodyned array of Michelson interferometers (MIs) in a silicon-on-insulator (SOI) platform. We demonstrate that with the same progressive geometric path length difference between the spatially heterodyned arrayed interferometer arms, MIs double the optical phase delays and thus double the wavelength resolution (δλ=0.8nm) compared to Mach-Zehnder interferometers (MZIs) (δλ=1.6nm). Our proof-of-concept device demonstrates one method to address the bandwidth-resolution tradeoff inherent in on-chip FTIRs, which gains in significance for optical sensing applications requiring single digit picometers resolution in compact on-chip form factors.

We report on a compact, on-chip, and inexpensive Raman spectrometer platform that provides 6 orders of magnitude enhancement of Raman signal in the near-IR spectral range of 0.7-1.2μm with a laser excitation of 785 nm. It is based on microring resonators integrated with sinusoidal photonic crystal (MRR-SPC) both in the ring-resonator and in the bus waveguide. A low-loss Si₃N₄ waveguide is chosen to meet the requirements of high index contrast and ultracompact design. The proposed MRR-SPC can find its applications in bio/chemical ware fare sensing, chemical sensing, lab-on-a-chip systems for mobile and portable devices.

We introduce a compact spectrometer based on a new optical component – rotated chirped volume Bragg grating (r-CBG) – with a compact footprint capable of spatially resolving the spectrum without the need for subsequent free-space propagation. Unlike conventional chirped Bragg gratings in which both the length and width of the device increase with operation bandwidth, the link between the length and width of r-CBG is severed, leading to a significantly reduced footprint for the same bandwidth. We fabricate and characterize such a device of total volume 25x6x6 mm3 in multiple spectral windows, we study their spectral resolution, and via FROG measurements we confirm that a pair of cascaded r-CBGs can resolve and combine the spectrum of a 100-fs pulse.

We present a novel cost-effective high spectral resolution and small bandwidth spectrometer for the fiber optic frequency domain optical coherence tomography (FD-OCT) for thin wafer semiconductor applications. The spectrometer employs achromatic dispersive optics. We also present a novel method for calibration of this narrow bandwidth spectrometer using a fiber optic Michelson interferometer.

Filter-based spectral detectors convince with their simple concept, an extremely compact and robust design and the possibility to adapt the addressed spectral range and the resolution to the individual application requirements. Unfortunately, these filter-based sensors usually suffer from low detection efficiency. In this contribution we discuss and compare different methods that allow to substantially increase the detection efficiency of filter-based spectral sensors. An initial concept is based on a wavelength-dependent redistribution of the incident light before it reaches the individual filter elements of the array. This approach allows a substantial increase in detection efficiency, but requires additional dichroic elements in the beam path. An alternative approach uses a folded beam path architecture and completely waives additional dichroic elements. This approach is not only suitable for filter-based spectral sensors, but can also be transferred to increase the efficiency of hyperspectral imaging systems.

We present a novel miniaturization strategy that allows us to create versatile compact Raman spectrometers and microscopes based on cheap non-stabilized laser diodes, densely-packed optics, and non-cooled small pixel size sensors. We demonstrate that the achieved performance is comparable with expensive and bulky research-grade Raman systems. Our miniaturization concept is based on real-time calibration of Raman shift and Raman intensity using a built-in reference channel that is independent of the main optical path.

This paper introduces a fluorometer that is both economically viable and optimized for sensitivity. The sensor is designed to detect low concentrations of fluorophores in the visible spectrum range, utilizing a deep ultraviolet (DUV) 275-nm LED and a dichroic mirror to establish a co-axial optical path for excitation and emission. Unlike traditional general-purpose spectrometers, this sensor achieves a balance between the two through an appropriate aperture size and tailored optical design optimized for the spectral characteristics of fluorophores. The manuscript presents measurements of rare earth element (REE) samples containing terbium (Tb), europium (Eu), dysprosium (Dy), and samarium (Sm) in aqueous solutions at ppb-level concentrations. By optimizing the collection of fluorescence emission without sacrificing spectral information, this work demonstrates the feasibility of developing a low-cost, compact, and highly sensitive fluorescence sensor that is comparable to bench-top commercial spectrofluorometers at a fraction of the cost.

Sensors and micro-instruments that can be used for measurements on-site are required primarily due to applications regarding the Internet of Things (IoT), or Industry 4.0, and to a lesser extend for the need to “bring part of the lab to the sample” (e.g., for analytical or chemical measurements in the field). Ideally, for field sensors and instruments they must be operated from energy harvested from the ambient (instead of using a battery). One example is by employing Tribo Electric Nano Generators (TENGs). In my lab, we have been working on TENGS for a number of years, continued work and further developments TENGS will be described here.

For some applications, resonant cavity infrared detectors (RCIDs) offer advantages over traditional broadband photodetectors. The addition of a resonant cavity allows for higher external quantum efficiency (EQE), faster response time, and narrower spectral response for enhanced selectivity. Recently, the US Naval Research Laboratory demonstrated RCIDs with EQE of 34% and D^∗ of 7 × 10⁹ at room temperature, centered at 4.0 μm (46 nm FWHM). Princeton University has demonstrated that these RCIDs can detect gas-phase nitrous oxide (N₂O) at room temperature with only a broadband light source and no other optical components. The results imply that a simple RCID-LED pair manufactured on a semiconductor wafer would provide a viable gas sensor. The manufacturing process could be completely automated, resulting in mass-producible optical gas sensors. Progress has been made for developing RCIDs at other wavelengths. Based on the achieved detection limit of 4% N₂O at 4.0 μm, with 3 cm path length, leak detection of percentage-level concentrations of gases is definitely viable. The potential for operating at a more optimal wavelength to attain high-precision measurements at part-per-million (ppm) levels is still under investigation.

A novel technique using a W-band metasurface for the purpose of transmissive fine powder layer sensing is presented. The proposed technique may allow for the detection, identification, and characterization of inhomogeneous ultrafine powder layers which are effectively hundreds of times thinner than the incident wavelengths used to sense them. Such a technique may be useful during personnel screening processes (i.e., at an airport) and in industrial manufacturing environments where early detection and quantization of harmful airborne particulates can be a matter of security or safety. Recently, characterizations of ultrathin powder layers using a novel metasurface sensing technique have been conducted at W-band1. Finally, a novel technique utilizing this metasurface will be presented, which could aid in the characterization of various dilute dielectric materials in solutions.

We introduce an optical spectrum analyzer that relies on the linear relationship between optical frequency and the Brillouin frequency shift (BFS) in optical fiber. To measure the Brillouin frequency shift, we use the signal under test as a “pump” to excite Brillouin lasing in a fiber ring cavity and use self-referenced heterodyne detection to measure the frequency shift of this Brillouin lasing mode. We present the basic operation of the system and demonstrate wideband measurements over ~48 nm with 20 MHz (0.16 pm) resolution at a measurement rate of 10 kHz.

Polarization conversion devices which can manipulate the polarization status of electromagnetic waves are essential to various areas of photonic applications such as communication, imaging, and remote sensing. Due to its wide bandwidth and high penetration through dielectric materials, THz wave, range from 0.1 to 10 THz is increasingly popular for noninvasive screening, high-resolution imaging, and more precise data collection. Metamaterials (MM) are artificial materials fabricated from repeated arrays of subwavelength-sized meta-atoms, and MM-based THz polarization conversion devices can be thin, extremely compact, easy to integrate, and even flexible, unlike conventional polarization devices. In light of that information, we utilized a stereo-metamaterial (SMM) structure for new-generation THz polarizers converting the polarization from linearly to circularly and elliptically polarized wave at the THz frequency range in reflection mode. In this work, we present the processes and results of the inverse design of SMM using the artificial neural network (ANN), trained by various parameters, including polarization status and ellipticity angle, to achieve highly efficient device performance. Training and testing our ANN with the created datasets by simulation for the inverse design of the device, design parameters were obtained by giving an artificial EM response or ellipticity angle spectrum or vice versa more efficiently and rapidly. With the device fabricated based on the ANN-powered design, we demonstrated effective sensing of different polarization statuses using THz polarimetry spectroscopy.

Nanohmics has recently developed a compact tunable filter for the longwave infrared that is based on a novel tunable plasmonic metasurface. Due to its high throughput, we are pursuing multispectral imaging on uncooled detectors that would normally be too light starved to operate with typical bandpass filters. We will present preliminary demonstration datasets and our progress integrating the filters with handheld imaging systems.

The need to rapidly detect, locate and repair natural gas leaks from natural gas infrastructure has become ever more urgent since methane is recognized as a potent greenhouse gas and is contributing to the global climate change. An optical gas sensor based on mid-infrared lasers and the method of backscattering tunable diode laser absorption spectroscopy is developed and provides gas concentration measurements with parts per billion by volume sensitivity. Ethane is a secondary component of natural gas. Concurrent methane and ethane measurement discriminates natural gas from biogas. The ability to approximate emission rate and leak location helps to prioritize repairs. This dual-gas optical gas sensor weighs about 2 kg, is battery-powered and is designed to be easily installed and removed from survey vehicles. A scattering target placed 1-m away from the gas sensor unit provides an open-path configuration for the laser beams to analyze ambient air. While the vehicle is traveling at 10 m/s, this gas sensor package is sensitive to cm-scale gas plumes due to a sample frequency of 100 Hz with data output rate at 10 Hz. Gas concentrations, GPS, and wind information along the survey route are collected wirelessly and processed with a computing tablet. Cloud-based data analytics further process the survey data. Early blind survey testing covered 54 natural gas leaks and 7 sewer emissions. Nearly 100% find rate for all true natural gas leaks was achieved with very low false positives and negatives. Leak indications were verified with follow-up survey with boots on the ground.

Physical Sciences Inc. (PSI) is developing a sensitive, rugged, person-portable, and safe instrument for the quick analysis of metals in jet fuels in fuel depots and transfer stations. The instrument fills a needed role for easy and affordable analysis of catalyzing metals content in fuel batches before they are used in, or shipped to, critical engines such as military aviation platforms. The instrument targets a panel of most likely and problematic metals that are often found in kerosene-based fuels, both refined and synthetic. The cause for concern lies in the potential for many metals, even at part per billion (ppb) concentrations, to catalyze rapid degradation of fuel performance, especially at elevated storage temperatures. The laser-induced breakdown spectroscopy (LIBS) technology development reported here has demonstrated a robust and viable measurement system for multiple contaminants of importance to military (and commercial) fuel distribution. Estimated detection limits for all elements of interest, save phosphorus, are at sub-ppm levels. Signal normalization with an added internal reference has demonstrated an adjusted concentration measurement accuracy <95% and useful operation of the method near the noise floor of the instrument. The accomplishments are strong indicators for commercial potential for the technology as a useful tool in the intended fuel monitoring application, as well as other industrial sample analysis needs.

There are 100,000’s of oil and gas storage tanks and tank batteries at upstream production sites. These sites have shown to be inadvertent, intermittent, generally unmonitored, high flow rate (flux) methane emitters; their emission rates are poorly quantified. Flux measurements are inhibited by the difficulty to directly access emission sources, instrument limitations and high-cost, and inability to distinguish between unintentional fugitive emission events (leaks) versus routine venting from pneumatic valves and compressors. Novel cost-effective and reliable continuous quantitative methane flux measurement technologies are needed to address these challenges. Methane is a potent greenhouse gas, and emissions from these sites need to be detected and prioritized for repairs based on emission rates. This paper describes a continuous methane emission monitor that combines our easily-installed high-speed laser-based long-open-path sensor, the Remote Emissions Monitor (REM), with a unique and novel fast laser beam scanning mechanism to create “flux planes” along site perimeters. This Enhanced REM (eREM) directly measures and reports emission rates (e.g. scfh) of methane plumes transported through the flux plane at about 1Hz without the need for plume modeling. The inherent temporal resolution enables novel statistical data processing that identifies routine vents and distinguishes them from unintended emissions. The simplicity of design, ease of installation, and minimal maintenance enable economically attractive fast and accurate detection and quantification of methane leakage.

We developed a prototype portable LWIR hyperspectral system based on a commercial microbolometer array and a spectral interferometer to test its utility in the field. The complete system with sensor head, tripod, scan motor and batteries weighs 10.5 lbs. Field tests show peak SNR near 250, and spectral analysis was able to detect specific minerals at geologic sites in Arizona. The project showed the feasibility of very low cost LWIR hyperspectral systems.

We present the results of characterizing and using a quantum cascade laser as a broadband infrared source for real-time spectroscopy. Using a Fabry-Perot quantum cascade laser (FP-QCL), we illuminate samples with “white” light from 8.2μm to 10.2μm. This laser source and its operating conditions (25°C and 500ns pulses at 200kHz) were chosen to give broad spectral coverage and high power output (42.7mW average power, pulsed operation). We utilized a simple grating spectrometer together with a micro-bolometer focal plane array to capture each full spectrum in a single frame. Several samples were characterized using this apparatus in a transmission-style measurement and their real-time spectra were compared to their Fourier Transform Infrared (FTIR) spectra. The results show a good agreement between FTIR and the real-time grating spectrometer for several exemplar samples, including bandpass filters, isopropanol vapor, and samples of IR active materials such as PTFE and polystyrene.

Copper indium gallium selenide (CIGS) thin film photovoltaic devices are in the early stages of large-scale commercialization. Their high performance, uniformity, reliability, and a low carbon footprint make them an attractive alternative to standard silicon solar cells. Due to the complex processing required and the associated manufacturing costs, reliable in-line quality control technology is needed. By identifying defective cells early in production, faulty batches can be excluded from further processing, saving resources and costs. We show that micro-Raman spectroscopy (RS) and hyper-spectral imaging (HSI) are powerful tools for quality control and process improvement. Distinctive features in the Raman spectra allow the estimation of the copper to gallium plus indium (CGI) ratio, which is an important criterion for the cell’s efficiency. With HSI in the visible and near infrared range (VNIR) and the near-infrared spectral range (NIR) in combination with machine learning techniques, the layer thickness and CGI ratio are accurately predicted.

This report describes inverse spectral analysis of diffuse-reflectance spectra measured using Infrared Backscatter Imaging spectroscopy (IBIS). In IBIS, a tunable infrared laser illuminates a target while an infrared camera detects the backscatter. Target analytes are identified by analyzing the pattern of absorption dips in the detected backscatter and comparing them to the known or simulated reflectance spectra of hazardous materials. The backscatter spectrum is comparable to diffuse reflectance measured using a Fourier transform infrared (FTIR) spectrometer. The analysis methodology applied here entails iterative adjustment of spectra using phenomenological backgrounds. and estimation of absorbance using the Kubelka-Munk (KM) theory of diffuse reflectance. Applying spectrum-feature enhancement, measured with a field spectrometer, can provide a better estimation of dielectric response, which is for comparison to reference dielectric functions, for identification of target materials.

The development of an ultra-compact, short-wave infrared spectrophotometer small enough to fit in a wrist-based wearable device produces the capability for non-invasive and real-time measurement of various physiologic biochemistries that cannot be interrogated with the same accuracy when using light emitting diodes (LEDs) and common photoplethysmography (PPG) applications. By producing many discrete and individually-generated light sources from tens of laser diodes on a single, silicon-based photonics integrated circuit (PIC), this new platform enables us to determine a user’s body temperature, hydration status, and concentrations of solutes within the dermal interstitial fluid, potentially useful in monitoring health in a novel way.

Raman spectroscopy was used to measure the temperature of semiconductor test structures. The structures consist of molybdenum microwires on a Si (100) substrate buried under a 270nm layer of aluminum nitride. The temperature-dependent Raman spectra of the examined materials were measured in a temperature range from 30 °C to 450 °C using a scientific grade temperature stage for calibration. The relationship between the structure’s temperature and its Raman peak position was modeled. This model was used to estimate the temperature distribution across the test structure at different operating powers with high spatial and temperature resolution.